David Martin, head of Herbert Smith's tax section, assisted Walker-Arnott in the case.

He says the firm took the unusual step of dispensing with counsel because “we felt [Walker-Arnott] could do at least as good a job as counsel.

“He is clearly someone who would be very good before the High Court, because he has the sort of presence that would go down well”.

Martin adds that the ruling is of “widespread importance” because it affects companies and individuals who prepare accounts under generally accepted principles. He says it confirms and “gives further assurance that those principles will apply for tax purposes”.